Process for producing aquecus solutions of free cyana lid



OFFlCEi ZCDGJEI NEW JERSEY, ASSIGNUR TO EGALL U TUBE, N. Y., A CORPORA- .uiis iiccii in l WAG comic; 0. file .rcuction so slow at or c i. coinmci rec iliiiary or we that ii is (lillicull; i'o prevent not well uowii. local alkalinity in lhc solution with couscle-" iiies own-1i RllQtilOClrl of ut culling down of yield. If carbon diiuc l arc i: run into the calcium cyanamiil solulion lion or pension under pressure. the ap- 'jliliiilllS neccseziry is complicated and Lliilicult n lo (morale. mugii go I 1 lily inrcniion obviates all the ahove (lifi unilcrial ohif licullirs hy simply passing sulphur dioxide neulralim gram or mixml containing sulphur (limu oxiile or introducing Sodium or calcium hi- 5}; 21mg Y aul 'iliil'e or o'lher soluble oisulphiies at proper rate into a suspension or solution of pow- :lercd coimtocrcinl calcium cyamin'iicl in water 6 in :i suitable vessel, for example. in an orcliuar javlicled kettle- Wilh a good mechanical loin, the kettle heinossuiiiciently cooled ruining water. The reaction bcliwcen 'lioxicle and calcium cyriainiil is 7' 3 riipulw so that there is no need of pics- ;cum. llirsm the sulphur dioxide forms sulrous acicl Willi the walcr. preseiil .02. U; his then rczicl's with the calcium crann- :1 rec; truliz; 1., with 19 extracting; oilicr pro i solution or am" loy slroui: :1 with cal-lion all ll'iesc proc" in moral yicu equipment 1:5 crig'icnsive S, trol.

If ihc. NilCi'll", 20 comes loo iicirlic, lyzcd lo urea.

Yo procw Milli. if:

and lliv or-mi may li o monimii. c olm'l'c, tho

l-lulvhm' (lionizle living or: acidic one i i M3 5 of i 1 "forming sulphurous ZHlll with 'n'itci', as above 80 polyniem 'm ilH'jmHlfiUliK-l7 chow'n, here 15 no i'rouhle as to thc r'ziclion 1 i i f? i 530MNELIIUSliAHg oecoiino allmlmc. Sulpliuious acid being weak sicid, the rise iii icmpemlure is not 11 w, "1 7 al J. Ii. lie uellllmflilllllfil ww Loo high, mil; l c beyimd mi For same magma the above i'cz clioiis :iro consulcroli accelero't J and if the solution not ileifil f l calcium cyauzimiil acts; as if it. hydrolyzes to calcium carhoiszilc zmu :iiiimoiiui:

iuven i more sulphur dioxide added In muirulizalion wit 'ic with 3 water pit-25ml; lilo calcium 2. z 1 '1 dissolvci; iilhfl 1 illll'lOll beasily the o5 .iiiiiili "T armcthere ocel or i'ieoirzil,izetion will-1 mixingac.

acidity will not lie Vci'y great under the most S5 pnuric acid, i is p- ;u cyii i the excess merely forms cal- EMT-TED? re hisul i-hil'e instead of calcium sulphitei ("ion oi calcium rrmiuiiiiid bisul'pl ilo is formed Wllflll too much rise in lernpcmune. my is being sii ggplicci for still acidic enough so capacityof the kettle and too much in pro portion to the efliciencyiof agitation iilicl coolmg: 7 V

-'oiiou ugo-resin:

' The calcium bisul )hite so formed is eveui a tuallv used u in the reaction. usr. as sulhur dioxide or sulnhurous acid:

CaCN +Ce (H50 zCNNl-L-kQGaSQ,

The soluble calcium bisulphite is a partially neutralizedsulphurous acid, and, by its formation it acts as a bufier against too great acidity. The sodium or calcium. bisulphite or other soluble bisulphites are that they may be used as reagents "for liberating free cyanomid from calcium cyanan'iid, if desired.

The calcium sulphilc finall iorincil rcn'iains u. an easily filtered precipitate along; with the insoluble ilnpuriliics of the connucrrial calcium oyananiiil. and the free cymnuniil goes into solution in the water supplied. As the calcium cyanamiil in powdered form, or its Water solution, i= added to the water being treated with the sulphur dioxide, as above explained, there will come a stage when the slurry will be too thick for further agitation. At this stage, the contents: of the kettle are tapped oil and lillcrcd. uiu'l lhc filtrate and 'ushings rcturncd lo the lHlllO for a second continuous trcalnu-nl with more calcium cyunzuniil in powcilrcil form or in water solution. {Hill more sulphur (ll().\l(l(. This procedure is rcpcalcil until maximum concentration of tree C \zll1l\llll(l in proportion to yield is obtained. in water solution.

The solution of free cvanuniirl thus produced will he practically pure anal a strength of approximately 13 CN.NH. may easily be ohtaincil. ll ig'hcr concentrations can be prepared, il ilcsircil. Duriug'thc operation oi the proccss. the acidity should he held (lown closc to nontrality. Absolute iicutralitv is that cmulltion of a solution at which the concentration of the hydrogen and lryclrhxyl ions is the same, i. e. 10". However. it is not ncccssary that I maintain cxactly this neutrality.

Due to the fact that I)l](lllll]lllillillllll changes at PM or rather over :1 i'augc from 11,8 to Pull) it. is very suituhlc as an indicator for Weak acids and I prefer to use its color change as my point of approximate neutrality (luring thc reaction, preferably nniintuining lhc .\(llllll lil just on the acid sirlc.

As simple examples of my invi'rntion T shall now describe two cxpcriincnts which i nnulo, which illustrate one method of carrying out my process.

Ewampi'e 160 cc. of water were maintained at not over 40 0., as above clescribed, and a total of 210 5; H1115 of calcium cyanamicl, pure, powdered to 50 mesh meet/e1 wus aihlcil in four stages, 52.5 grams at each stage. with filtration and. return of filtrate and washings ailcr each stage, snlpl'iurous a itl in i lll'lll of sulphur ilioxiile havinghccn :uhlczl to complete precipitation of the cal- ('llllll as nculrul sulphitc (luring ouch stage. The lirsi liltrulc conluincil 6.74% CXNH lhc. scconil. flflllj; the thinl, 1 .03%; and the 'l'ourlh liltraic conluincd 13.5% of Chhhll l The precipitate in each stage occluded about fill cc. of "alter and the precipitate in each stage was washed with about 50 cc. of \Yntcr. to bring the voluruc of the liltiuio lo 400 cc.

[from 17c fir ll'iill the sonic quantities and method of operation as in Example I. exceptthat thc calcium cvanainid was added in live shugw inszlinul of four, grams to a'slairc, the lirnl lillrul" contained 4.35" UNNHQ; thc noconrl 456; the lllll(l, M18575); the fourth. 12.35): and the fifth lillrule contaiucil 153.5% Clllill l (lo not limit niyscll to any particular proportion of calcium C VflI!i1l1ll(l lo wulcr uscil. nor to un epccilicil temperature or degree oi acidity. The more water used, the lower will he the ilnupcruturc. The lowcr the temperature and the acidity, the better will he the yield of (FNNH The more cilicicnt the agitation. the higher will he the maximum per cent (f-NJflI-l obtainable in the lust til-irate and the better will be the yichl of llYNl-l... bllSNl on (MUN in the raw material. l (in not limit myself to any particular ilcgrcc. of lincncss of the calcium cyananiiil pi'iuilcr. If pim'clcrcd too linc, the auction may proceed too fast; if not ])()\\'(lll'((l sullicicnlly line, too great agita tion will he acquired to maintain a suspension in water.

it has alrcady hccn explained that sulphur (lioxhlc. though Very convenient to use, (loci-i not lulu: part as such in tho chcmicul rcactions involved in my invcnlion, since it is chungcil almost at once to sulphur-nus uciii upon coining in contact with water and since hydrogen is necessary to any reaction that forms (.yanarnid:

lliOl--F-W). .::ll3(l 'lhc cquzrt ion:

it sodium hisulphilc is uscrl us a source oi sulphurous acifl. there will he rcquircrl 1.62.) tiincs as much sodium hisulphitc by weight as of sulphur riioxiric. The collation illustrating its use is as follows: CaCll l-QNuHSfi it is obvious that in practising my invention, I do not need to limit myself to the use of any particular source of sulphurous acid. Therefore, in the appended claims, treatment withsulphurous acid is to be interpreted as including the introduction ot sulphurous acid'in the form'ot' the gas sulphur dioxide, the" use of solutions containing dissolved sulphur dioxide or sulphurous acid, or ofsolutions of'acid sulphites.

Only standard equipment is required in the operation of my-process. This includes means to be provided for so distributing the gaseous sulphur dioxide or the solution of sulphurous acid as to avoid excess local acidity in the calcium cyanamidslurry and means to be provided for adding the calciumcyanamid to .the water used, so as to avoid excess local alkalinity in the slurry thus produced.

1 do not limit myself to the use of calcium 'cyanamid since I can operate with the cyanamid of any other metal, whose neutral sul- 4 phite is insoluble in water.

What I claim'is:

1. The processof producing a solution o't' cyanamid consisting in treating a solution of metal cyanamid with sulphurous ,acid under such conditions that the liquid remains substantially neutral in .reaction and metal sul-' phite is precipitated.

2. The process, consisting in treating a metal cyanamid solution with sulphurous acid at such rate and at such temperature while maintaining the solution substantially neutral as to form cyanamid in solution and precipitate the metal sulphite.

3. The process of producing a solution of cyanamid consisting in treating a solution ofcalcium cyanamid in water with sulphurous acid, filtering and washing the precipitate, and treating the combined filtrate and washings with fresh supplies of calcium with fresh supplies of calcium cyanamid and'sulphur dioxide, until a filtrate of the desired concentration of CNNH has been obtained.

5. The processor producing a solution of cyanamid consisting in passing sulphur dioxide into a solution of calcium cyanamid in water that is being cooled and agitated, at such rates that the liquid remains substantially neutral in reaction, then filtering and washing the precipitate and treating the combined filtrate and washings with fresh Supplies of calcium cyanamid and sulphur dioxide, until a filtrate of the desired con-- centration of CNNH has been obtained,

6. The process of preparing cyanamid consisting in. treating a metal cyanamid and water with sulphurous acid, separating the solution from the precipitated metal sulphite, and treating the solution with additional metal cyanamid and acid.

7. The process of concentrating a solution of cyanamid, which consists in forming cyanamid in solution and a precipitate, separating the solution, treating the 7 solution with a metal cyanamid and sulphurousacid, and separating the precipitate Signed at Perth Amboy in the county of Middlesex and State of New Jersey this -8 day of August A. D. 1924.

ANTHONY MOULTRlE MUCKE NHJS S. 

